Topic 12 - chronic venous disease Flashcards
What are the two main types of valves?
• ostial and parietal
What is an ostial valve?
o form at the opening of venous tributaries
o These valves occur at the confluence of tributaries as they drain into the deep veins or main superficial veins but prevent back-flow into the tributary.
What are parietal valves?
o form in the vein segments between the tributaries and are typically bicuspid or tricuspid in the lower limb.
o These valves prevent the extended back-flow or reflux of blood following augmentation by calf muscle pumps.
o The number of parietal valves present in the deep or superficial veins of the leg varies
What is chronic venous disease (CVD)?
covers a range of changes in the veins, skin and lymphatic drainage
What are some symptoms of CVD?
symptoms ranging from mild itching and swelling to severe ulceration of the skin.
What is a contributing factor to CVD?
• Venous Incompetence
What are changes in the vein wall during CVD?
- loss of endothelium
- inflammation
- neovascularisation (particularly associated with ulcers)
- increase in wall thickness
- fibrosis of the wall
- loss of smooth muscle function
- destruction of the venous valves
What are some hemodynamic and physical changes of CVD?
- loss of calf muscle pump efficiency
- stasis of the limb venous blood pool
- Loss of ankle motion
How is venous flowmaintained?
Supine -
• Without the effect of gravity on the veins, venous flow is generated by the pressure difference between the heart and the periphery.
• This is generated by the capillary flow and can be measured at about 15 mmHg.
Standing -
• On standing, gravity begins to increase the pressure in the veins in a direction opposite to that of the normal venous flow direction.
• Venous valves simply prevent blood volume (mass) from returning toward the foot.
• The calf muscle pumps assist us to actively return blood to the heart whilst in a standing or partially standing position
Where are the lower leg muscle pumps located?
- Foot (augments on standing or walking)
- Calf
- Thigh
How does venous pressure change while walking?
- During normal locomotion, blood is pumped during the active contraction of the leg muscles and the venous pressure reduces.
- At times when the majority of the muscles are relaxing, the venous pressure rises due to the lack of augmented flow and refilling of the empty veins form capillary flow.
- As the heel returns to the ground, it takes about 25seconds for the venous pressure to return to resting values
How is venous pressure affected while walking in a patient with CVI?
- the augmentation of the blood by the muscle pump may be impaired, thus causing less fall in pressure than expected or no pressure fall at all.
- During the stages when muscles are relaxed, an incompetent venous system will allow a greater volume of blood to return (or fall) back into the veins and return the venous pressure to that of a standing person more quickly.
- Both the impairment of the calf muscle pump and quicker filling of the veins causes the venous pressure to be higher (reduced less) than in a normal person.
what is Ambulatory Venous Hypertension ?
- ‘raised’ venous pressure is termed Ambulatory Venous Hypertension and is often referred to as ‘venous hypertension’ in many texts.
- It does not represent a pressure which is higher than that seen in a standing and stationary person, but it is higher than expected from a person with normal functioning veins.
What causes ulceration?
Venous hypertension causes a chronic elevated pressure in the post-capillary venules and this leads to damage of the capillaries and possible ulceration.
What are the risk factors for varicose veins?
- Young and female
- Older and male
- Family history of varicose veins
- Pregnancy
- Giving birth to 3 or more children
- Having experienced a deep vein thrombosis in the past
What are he main symptoms of CVD?
- skin pigmentation (discolouration)
- Itching
- weeping dermatitis
- ulceration
- lipodermatosclerosis
- swelling
- heaviness of the leg
- aching
What are the non surgical options for treating varicose veins?
- The most important and effective - compression bandaging and stockings.
- Venoactive drugs
What are the surgical options for treating varicose veins?
• Direct surgical disruption of the incompetent veins or ablation with chemical, thermal, laser or mechanical devices
What is the purpose of ultrasound examination of CVD?
• to identify which veins are refluxing and where those veins communicate to the deep veins and to other superficial venous systems.
essentially a mapping process
What are the different networks of veins?
- posterior thigh
- anterior thigh
- medial thigh
- posterior and lateral calf
What are accessory veins?
The great, small and anterior accessory saphenous veins run in defined fascial sheaths.
Once outside these fascial planes, they are termed accessory veins of whichever saphenous vein you are looking at.
What is venous reflux?
• Reflux is the abnormal back-flow or retrograde flow of blood in a given vein
What measurement signifies reflux?
• The terms reflux or significant reflux are generally accepted as retrograde flow lasting longer than 0.5s in the superficial veins and longer than 1.0s in the deep veins.
What are perforating veins?
- By convention the perforating veins direct blood from the superficial to the deep veins in order to maximise the efficiency of the calf muscle pump.
- However, some perforating veins are valveless and others are known to direct blood toward the superficial veins
